package com.tk.exam.utils;

import sun.misc.BASE64Decoder;
import sun.misc.BASE64Encoder;

import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import java.security.Key;
import java.security.SecureRandom;


public class DESUtil {
    private static Key key;
    private static final String ENCRYPTOR_KEY = "QyP1CnvpfxtrV1BX2C7zhgn3vh6azhV3";
    // 设置密钥key
    private static String CHARSETNAME = "UTF-8";
    private static String ALGORITHM = "DES";


    private static void generatorKey(String password) {
        if (key == null) {
            try {
                // 生成des算法对象
                KeyGenerator generator = KeyGenerator.getInstance(ALGORITHM);
                // 运用SHA1安全策略
                SecureRandom secureRandom = SecureRandom.getInstance("SHA1PRNG");
                // 设置密钥种子
                secureRandom.setSeed(password.getBytes());
                // 初始化基于SHA1的算法对象
                generator.init(secureRandom);
                // 生成密钥对象
                key = generator.generateKey();
                generator = null;
            } catch (Exception e) {
                e.printStackTrace();
                throw new RuntimeException();
            }
        }
    }

    /**
     * 获取加密后的信息
     *
     * @param str
     * @return
     */
    public static String getEncryptString(String str) {
        //生成秘钥
        generatorKey(ENCRYPTOR_KEY);
        // 基于BASE64编码，接收byte[]并转换层String
        BASE64Encoder base64encoder = new BASE64Encoder();
        try {
            // utf-8编码
            byte[] bytes = str.getBytes(CHARSETNAME);
            // 获取加密对象
            Cipher cipher = Cipher.getInstance(ALGORITHM);
            // 初始化密码信息
            cipher.init(Cipher.ENCRYPT_MODE, key);
            // 加密
            byte[] doFinal = cipher.doFinal(bytes);
            // 返回
            return base64encoder.encode(doFinal);
        } catch (Exception e) {
            e.printStackTrace();
            throw new RuntimeException();
        }
    }

    /**
     * 获取解密之后的信息
     *
     * @param str
     * @return
     */
    public static String getDecryptString(String str) {
        //生成秘钥
        generatorKey(ENCRYPTOR_KEY);
        //基于BASE64编码，接收byte[]并转换成String
        BASE64Decoder base64decoder = new BASE64Decoder();
        try {
            //将字符串decode成byte[]
            byte[] bytes = base64decoder.decodeBuffer(str);
            //获取解密对象
            Cipher cipher = Cipher.getInstance(ALGORITHM);
            //初始化解密信息
            cipher.init(Cipher.DECRYPT_MODE, key);
            //解密
            byte[] doFinal = cipher.doFinal(bytes);
            //返回解密之后的信息
            return new String(doFinal, CHARSETNAME);
        } catch (Exception e) {
            e.printStackTrace();
            throw new RuntimeException(e);
        }
    }

    public static String getEncryptPassword(String password){
        return MD5Utils.MD5(getEncryptString(password));
    }


}
